It is known to employ energy exchange technologies in order to, for example, recover excess heat energy from an air-conditioning system to provide energy to heat water. Many examples of such heat-exchange technologies came about in the early 1980s which reflect the end of the energy crises of the 1970s. It is interesting to note that these heat-exchange technologies have not been generally adopted.
Existing solutions do not provide precise and robust control adequate for heat recovery systems, given that waste-heat recovery typically has large temperature gradients of the kind unforgiving to poor control.